Part 6

Fluorspar, or fluorite, is a glassy mineral that is commonly gray, white, or colorless, but may be green, blue, purple, yellow, or black. It is composed of calcium and fluorine. Fluorite is not a gem because it is too fragile and soft. Mineral collectors seek it because it is attractive and because some varieties have the ability to glow under invisible ultraviolet light (hence the term “fluorescence”).

WHERE ARE FLUORSPAR DEPOSITS LOCATED AND HOW IMPORTANT IS ILLINOIS PRODUCTION?

Fluorspar produced in the United States comes chiefly from a small area in Illinois and Kentucky where it has been mined since 1842. Illinois produced about 66 percent of the nation’s total in 1963. The state’s production amounted to more than 132,000 tons, valued at about $6,547,000. The crude ore is extracted from nearly horizontal bedded deposits and from nearly vertical veins in mines up to 800 feet deep in Pope and Hardin Counties. Finished fluorspar is produced from the crude ore by separating and concentrating methods.

WHAT ARE FLUORSPAR PELLETS?

In the separation of fluorspar from the other materials with which it naturally occurs, a process is used that involves grinding the spar to a very fine powder. The powdered spar has a number of uses, but to suit it for use as a flux (a substance which promotes fusion) it is made into pellets by the use of a binder.

WHAT IS FLUORSPAR USED FOR?

Fluorspar is used extensively as a flux in the steel industry, but over 50 percent of the spar produced in Illinois in 1963 was consumed in the manufacture of hydrofluoric acid. A large portion of this acid production is used in the aluminum industry. Hydrofluoric acid is also employed in the preparation of many fluorine compounds, particularly those used in the production of fluorocarbons (refrigerants, plastics, aerosols), insecticides, and high-energy fuels for rockets and missiles. The fluorocarbons utilize about 40 percent of the hydrofluoric acid production.

LEAD AND ZINC

WHAT ORES YIELD LEAD AND ZINC IN ILLINOIS?

The mineral galena is the principal ore of lead. Galena is gray in color, very heavy, has a bright metallic luster, and breaks into cubes along steplike cleavage surfaces (fig. 18). It is composed of lead and sulfur.

The chief ore of zinc is the mineral sphalerite. It may be brown, yellow, or black. Sphalerite is a combination of zinc and sulfur, has a resinous luster, and is not as heavy as galena.

WHERE ARE LEAD AND ZINC MINES LOCATED AND HOW LONG HAVE THESE ORES BEEN MINED?

Although the lead deposits of extreme northwestern Illinois (now Jo Daviess County) were reported by the French explorers in 1658 and are said to have been worked by the Indians, the influx of white settlers in the early 1800’s marked the beginning of an extensive mining industry, which was an important factor in the early development of that part of the state. The town of Galena takes its name from the mineral galena, which was the principal ore mined.

In 1845, the Upper Mississippi Valley produced 60 percent of all lead mined in the United States, which then ranked first in world lead production. Until about 1860, the zinc ore was considered useless, but today its total value is several times that of lead.

Lead mining began in southern Illinois in 1842. Lead and zinc production in this area is a by-product of fluorspar mining.

WHAT IS THE VALUE OF THESE METALS PRODUCED IN ILLINOIS?

In 1963, Illinois produced 20,377 tons of zinc valued at about $4,677,500 and 2,901 tons of lead worth about $626,600.

GROUND WATER

WHAT IS GROUND WATER?

Ground water is water that fills all openings in earth materials in the zone of permanent saturation. The top of the zone of saturation is called the water table. The source of ground water is precipitation (rain and snow) that seeps into the soil and percolates downward. Below the water table, ground water moves slowly toward places of discharge such as springs, lakes, rivers, marshes, and wells. Water falls to the ground, moves through the rocks, returns to the surface, and finally gets back to the atmosphere by evaporation and from plants (fig. 19). This cycle is continuously repeated.

WHAT KINDS OF ROCKS YIELD GROUND WATER?

Ground water is most readily obtained from saturated rocks that have fairly large openings between grains (such as sand, gravel, and sandstone) or have interconnected cracks or channels (such as limestones). Rocks that contain ground water and that will yield it to wells are called aquifers. Sand and gravel beds are widely used aquifers in Illinois.

EVAPORATION SAND AND GRAVEL WELL Water Table River sand and gravel ARTESIAN WELLS EVAPORATION River WELL COLLECTING AREA FOR ARTESIAN WATER PRECIPITATION Crater WATER TABLE WELL Lake Glacial pebbly clay Glacial sand and aquifer Shale Sandstone aquifer Limestone aquifer Shale GROUND-WATER RESERVOIR

IS WATER FOUND IN UNDERGROUND LAKES AND RIVERS IN ILLINOIS?

No. There are a few large springs that flow from rocks along river bluffs in Illinois, but most ground water occurs in tiny openings within the rocks. Ground water reservoirs may be regarded as similar to sponges rather than as underground lakes or rivers.

WHY DO WELLS SOMETIMES GO DRY?

The water table rises and falls seasonally and from year to year, depending upon the amount of precipitation. Sometimes the water table may fall below the bottom of the well or below the pump. Sometimes overpumping the well or pumping too many wells in a small area lowers the water table sufficiently to check the yield of the well.

WHAT IS AN ARTESIAN WELL?